Hebräer 5:5

glorified not himself--did not assume the glory of the priestly office of Himself without the call of God (Joh 8:54). but he that said--that is, the Father glorified Him or appointed Him to the priesthood. This appointment was involved in, and was the result of, the Sonship of Christ, which qualified Him for it. None but the divine Son could have fulfilled such an office (Heb 10:5-9). The connection of Sonship and priesthood is typified in the Hebrew title for priests being given to David's sons (Sa2 8:18). Christ did not constitute Himself the Son of God, but was from everlasting the only-begotten of the Father. On His Sonship depended His glorification, and His being called of God (Heb 5:10), as Priest.

In this chapter the apostle continues his discourse upon the priesthood of Christ, a sweet subject, which he would not too soon dismiss. And here, I. He explains the nature of the priestly office in general (Heb 5:1-3). II. The proper and regular call there must be to this office (Heb 5:4-6). III. The requisite qualifications for the work (Heb 5:7-9). IV. The peculiar order of the priesthood of Christ; it was not after the order of Aaron, but of Melchisedec (Heb 5:6, Heb 5:7, Heb 5:10). V. He reproves the Hebrews, that they had not made those improvements in knowledge which might have made them capable of looking into the more abstruse and mysterious parts of scripture (Heb 5:11-14).

5:5-6 The author brings Pss 2:7 and 110:4 together based on shared language—both passages have God speaking to his Son. The exalted Son, who came to earth as a human (Heb 1–2), is the one God has appointed to a unique high priesthood.